eneath the genital operculum (=sternum of the 1st somite of
opisthosoma).

[Illustration: FIG. 55.--_Thelyphonus sp_. Ventral view of the
anterior portion of the body to show the three prosomatic sternal
plates a, b, c, and the rudimentary sternal element of the
prae-genital somite; opisth 1, first somite of the opisthosoma.

(From a drawing made by Pickard - Cambridge, under the direction of
R.I. Pocock.)]

_Note._--The possibility of another interpretation of the anterior
somites of the mesosoma and the prae-genital somite must be borne in
mind. Possibly, though not probably, the somites carrying the two
lung-sacs correspond to the first two lung-bearing somites of
_Scorpio_, and it is the genital opening which has shifted. The same
caution applies in the case of the Araneae. Excalation of one or of
two anterior mesosomatic somites, besides the prae-genital somite,
would then have to be supposed to have occurred also.

Sub-order a. Uropygi.--Prosoma longer than wide, its sternal area very
narrow, furnished with a large prosternal and metasternal plate, and
often with a small mesosternal sclerite. Appendages of 2nd pair with
their basal segments united in the middle line and incapable of
lateral movement; appendages of 3rd pair with only the apical segment
many-jointed. Opisthosoma without trace of appendages; its posterior
somites narrowed to form a movable tail for the support of the
post-anal sclerite, which has no poison glands.

[Illustration: FIG. 56.--_Thelyphonus assamensis_ [male]. Ventral
surface of the anterior region of the opisthosoma, the first somite
being pushed upwards and forwards so as to expose the subjacent
structures. _opistho_ 1, First somite of the opisthosoma; opistho 2,
second do.; g, genital aperture; l, edges of the lamellae of the
lung-books; m, stigmata of tergo-sternal muscles.

(Original drawing by Pocock.)]

Tribe 1. Urotricha.--Dorsal area of prosoma covered with a single
shield (? two in _Geralinura_), bearing median and lateral eyes.
Post-anal sclerite modified as a long, many-jointed feeler. Appendages
of 2nd pair folding in a horizontal plane, completely chelate, the
claw immovably united to the sixth segment. Respiratory organs present
in the form of pulmonary sacs.

Family--Thelyphonidae (_Thelyphonus_ (fig. 54), _Hypoctonus_,
*_Geralinura_).

Tribe 2. Tartarides.--Small degenerate forms